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T. Bivona



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    MINI 09 - Drug Resistance (ID 107)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      MINI09.02 - Transcriptome-Metabolome Reprogramming of EGFR-Mutant NSCLC Contributes to Early Adaptive Drug-Escape via BCL-xL Mitochondrial Priming (ID 3085)

      16:50 - 16:55  |  Author(s): T. Bivona

      • Abstract
      • Slides

      Background:
      Precision therapy using EGFR small molecular inhibitors is the current standard-of-care in treatment of advanced non-small cell lung cancer (NSCLC) patients (pts) with EGFR mutations. Nonetheless, emergence of acquired resistance to therapy invariably occurs despite effective initial response. Classical rebiopsy studies of EGFR-mutant pts at clinical tumor progression based on RECIST criteria have identified diverse resistance mechanisms involving T790M-EGFR, MET amplification or activation and AXL upregulation. Tumor cells within minimal or microscopic residual disease during drug response may constitute founder cells for future disease relapse. The mechanisms of molecular changes intrinsic to these early therapeutic survivors are not yet well-understood. Our studies focus on tumor cells adaptation early during therapy to map the initial course of molecular drug resistance emergence and evolution.

      Methods:
      Drug-sensitive model studies of EGFR-mutant lung cancer were performed using HCC827 and PC-9 cells (exon 19 deletions EGFR) under erlotinib, and H1975 (T790M/L858R-EGFR) cells under CL-387,785 inhibition. Affymetrix microarray profiling was performed in triplicate at 0h, 8h, 9d and 9d tyrosine kinase inhibitor (TKI) followed by 7d drug-washout. Both in vitro and in vivo xenograft analyses, immunofluorescence, immunohistochemistry, time-lapse video microscopy analysis were conducted. Mass-spectrometry based global metabolomics profiling was also conducted under similar conditions as in gene expression profiling.

      Results:
      We identified an early adaptive and reversible drug-escape within EGFR-mutant cells that could emerge as early as 9 days during course of effective therapy with molecular drug resistance. Principal component analysis (PCA) of gene expression profiling data identified distinct transcriptome signatures in each cell state. Of note, the prosurvival cell state was independent of MET pathway activation, and had a TKI cytotoxicity escape at 100x higher IC50. The drug resistant cell state was associated with reversible cellular quiescence, suppressed Ki-67 expression, and profoundly inhibited cellular motility and migration. Transcriptome gene expression profiling revealed a remarkable adaptive genome-wide signature reprogramming, centered on the autocrine TGFβ2 cascade that involved pathways of cell adhesion, cell cycle regulation, cell division, glycolysis, and gluconeogenesis. Global metabolomic profiling of cellular metabolites in HCC827 cells under erlotinib inhibition also revealed a concurrent adaptive reprogramming of cellular metabolism during the early drug-resistant cell state, with suppression of glycolysis, TCA cycle, amino acids metabolism, and lipid bioenergetics. Our studies identified a direct link of TGFβ2 within the drug escaping cells, with the metabolic-bioenergetics quiescence, reverse Warburg metabolism and mitochondrial BCL-2/BCL-xL priming. Furthermore, this adaptive drug-resistant cell state also displayed an increased EMT and cancer stem cell signaling as adaptation to the drug treatment and that could be overcome by broad BCL-2/BCL-xL BH3 mimetic ABT-263, but not BCL-2 only mimetic ABT-199.

      Conclusion:
      We identified and characterized the emergence of early adaptive drug-escape within EGFR-mutant NSCLC cells amid an overall precision therapy excellent response, through a MET-independent mechanism. The profoundly drug-resisting prosurvival cell state undertook remarkable cellular transcriptome-metabolome adaptive reprogramming coorindated through autocrine TGFβ2 signaling augmentation. Our study results have important implications in lung cancer drug-resistant minimal/microscopic disease and future therapeutic remedies in precision therapy.

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    MINI 10 - ALK and EGFR (ID 105)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      MINI10.03 - Evolution of Concurrent Driver Mutations in Lung Adenocarcinoma Patients on EGFR TKI Therapy Uncovered by Comprehensive Molecular Profiling (ID 2848)

      16:55 - 17:00  |  Author(s): T. Bivona

      • Abstract
      • Slides

      Background:
      Lung adenocarcinoma (LAC) patients (p) with EGFR mutations respond initially to EGFR tyrosine kinase inhibitors (TKIs) but invariably develop acquired EGFR TKI resistance. Prior studies identified the EGFR T790M mutation and activation of MET, NF-kB, PI3K, AXL, HER2 and the MAPK pathway as drivers of acquired EGFR TKI resistance. We hypothesized that tumor cell populations present pre-treatment harbor mechanisms of EGFR TKI resistance that are subsequently selected for by EGFR TKI therapy.

      Methods:
      We performed longitudinal comprehensive molecular tumor profiling on 10 p with metastatic EGFR-mutant LAC throughout the course of their disease. Exome sequencing to a mean depth of coverage of 100 X, was performed on FFPE or frozen patient tumor specimens as well as matched normal control specimens collected from patients prior to initiating standard erlotinib (erl) treatment, upon the development of erl resistance, and upon resistance to subsequent 2[nd] line therapy when available. One case of a patient with acquired resistance to the 3[rd] generation EGFR TKI Rociletinib was analyzed. We performed functional analysis of select mutations identified using established cellular models of EGFR-mutant LAC.

      Results:
      We constructed phylogenetic trees based on somatic mutations and copy number alterations identified by exome sequencing of longitudinally acquired patient specimens. Activating mutations (L858R or exon 19 deletion) were present in all tumor specimens analyzed, indicating that this is a ‘truncal’ event. We identified on-target mutation in EGFR (T790M) in ~ 50% of erl resistant specimens as expected. However, in three patients we identified concurrent low frequency oncogenic driver events pre-EGFR TKI treatment that subsequently increased in frequency upon erlotinib resistance. This included: 1) a BRAF V600E mutation that was detected pre-treatment at a low frequency that expanded in the erlotinib resistant tumor specimen; 2) a PIK3CA G106V mutation that was not present in a patient’s primary tumor, but developed in a lymph node metastasis at a low frequency and subsequently expanded in the erlotinib resistant tumor, and 3) a pre-treatment KRAS amplification that was found in a patient with de novo resistance to erlotinib. The functional significance of these mutations in driving tumor growth and EGFR TKI resistance will be discussed. We will also present exome sequencing analysis from multiple tumors (including a CNS and spinal metastasis) collected from the autopsy of a patient with initial response, but rapid development of acquired resistance to Rociletinib.

      Conclusion:
      These results indicate that EGFR-mutant LAC can harbor additional oncogenic driver mutations at low frequencies prior to therapy. EGFR TKI treatment can lead to expansion of these subclonal populations likely contributing to EGFR TKI resistance in patients with or without the EGFR T790M resistance mutation. These data demonstrate the utility of comprehensive molecular profiling of LAC p on targeted therapy beyond assessing EGFR T790M mutational status, and suggest that pre-treatment tumor analyses can in some cases predict mechanisms of EGFR TKI resistance before they become clinically significant.

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    MINI 16 - EGFR Mutant Lung Cancer 2 (ID 130)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Treatment of Advanced Diseases - NSCLC
    • Presentations: 1
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      MINI16.15 - Discussant for MINI16.11, MINI16.12, MINI16.13, MINI16.14 (ID 3349)

      18:05 - 18:15  |  Author(s): T. Bivona

      • Abstract
      • Presentation

      Abstract not provided

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    MS 12 - NSCLC Stems Cells: Are They a Real Target? (ID 30)

    • Event: WCLC 2015
    • Type: Mini Symposium
    • Track: Treatment of Advanced Diseases - NSCLC
    • Presentations: 1
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      MS12.03 - Where to Go from Here? (ID 1902)

      15:00 - 15:20  |  Author(s): T. Bivona

      • Abstract
      • Slides

      Abstract:
      Lung cancer is a dismal disease, however, anticipated selective responses are observed in a subgroup of non-small cell lung cancer (NSCLC) patients where the disease is driven by epidermal growth factor receptor (EGFR) mutations. EGFR mutations occur in 15 – 40% of lung adenocarcinomas, according to gender, smoking history and geographical region. Two types of EGFR mutations account for 90% of all lung adenocarcinoma-associated EGFR mutations and are related to sensitivity to treatment with oral tyrosine kinase inhibitors (TKIs), such as gefitinib, afatinib or AZD9291: (i) small in-frame deletions in exon 19 that lead to elimination of an LREA motif in the protein (DEL) and (ii) a point mutation in exon 21 that substitutes an arginine for a leucine at position 858 in the protein (L858R). Lung cancer patients bearing EGFR mutations show radiographic responses to TKIs in 60 – 70% of cases. Although the majority of patients achieve a significant therapeutic benefit, almost all invariably progress in less than 1 year. Therefore there is an unmet medical need for novel therapies in order to avoid resistance to treatment. We have employed a wide array of approaches (MTT, western blot analysis, PCR, Aldefluor assay and mouse models) to demonstrate that the combination of gefitinib, afatinib or AZD9291 with compounds targeting signal transducer and activator of transcription 3 (STAT3) can suppress the mechanisms of early adaptive resistance. STAT3 is a member of a family of proteins responsible for transmission of peptide hormone signals from the extracellular surface of the cells to the nucleus. STAT3 is a master regulator of several key hallmarks and enablers of cancer cells, including cell proliferation, resistance to apoptosis, metastasis, immune evasion, tumor angiogenesis, epithelial-mesenchymal transition, response to DNA damage and the Warburg effect. In addition STAT3 promotes an increase in the cell renewal of tumor-initiating cells or cancer stem cell subpopulation, mainly aldehyde dehydrogenase (ALDH). EGFR mutations cause receptor oligomerization and activation of intrinsic or receptor-associated tyrosine kinases, respectively. These activated kinases phosphorylate receptor tyrosine residues creating docking sites for recruitment of cytoplasmic STAT3. STAT3 docks to receptor phosphotyrosyl (pY) peptide sites through its Src-homology (SH2) domain which leads to its phosphorylation on Y705 followed by STAT3 tail-to-tail homodimerization (SH2 domain of each monomer binds to the pY peptide domain of each partner). STAT3 homodimers accommodate in the nucleus, where they bind to specific STAT3 response elements in the promotor of target genes and regulate their transcription. EGFR mutations and tyrosine kinase-associated receptor interleukin-6 (IL-6) lead to the activation of STAT3 that is not obliterated by EGFR TKIs. Even more, 2 hours after starting gefitinib treatment there is an increase in STAT3 activation in EGFR mutant cell lines (P. Ma, Cancer Research, 2011). Moreover, following erlotinib treatment there is an enrichment of ALDH+ stem-like cells through EGFR-dependent activation of Notch3. We have tested several small molecules that target STAT3. The combination inhibits cell viability in several human EGFR mutant cells and blocks STAT3 activation. However, neither the combination of EGFR TKIs with TPCA1 (repurposed as a STAT3 inhibitor), nor the combination of gefitinib with AZD0530 (a Src inhibitor) prevent the increment in the ALDH + cancer stem cell subpopulation. Therefore, we are exploring more in depth the crosstalk between EGFR and IL-6. As a whole, human EGFR mutant cell lines have increased levels of IL-6 which leads to STAT3 hyper-activation. Nevertheless, recent evidence indicates that IL-6-Src can induce YAP activation and NOTCH signaling. The downstream effectors of YAP and NOTCH ligands CTGF and HES1, respectively, are being examined in clinical tumor samples. We have examined the combination of Src, YAP and NOTCH inhibitors in addition to the use of STAT3 inhibitors. The triple combination of gefitinib plus TPCA1 plus AZD0530 had great synergism with a very low combination index and also eliminated the ALDH+ population (Figure). Furthermore, the overexpression of ALDH1A1 was decreased with the triple combination, however with only gefitinib plus TPCA1 or gefitinib plus AZD0530, ALDH1A1 mRNA was substantially increased in comparison with gefitinib alone (Figure). The western blot for the triple combination shows the inhibition of STAT3 Y705 phosphorylation as well as the phosphorylation of YAP (Ser397) and also from BMI1. We plan to confirm some of the data in clinical tumor samples to understand the contribution of IL6 and well established effectors-the SHP2-ERK, PI(3)K-Akt-mTORC1 and JAK-STAT3 modules and the interaction with YAP. Figure 1



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